Consumption meters for measuring consumption data of a supplied utility, for example electricity meters, heat meters for district heating, and water meters for cold water, are often equipped with a communication unit for remote communication with the meter, and capabilities of being arranged in a communication network. Network enabled consumption meters greatly facilitates data collection, as well as remote control via transmission of control commands, and remote update via software upload.
Remote communication between a consumption meter and a central unit in a communication network can be obtained in a number of ways. Data is typically sent in the network by one of the standard means of broadcasting, multicasting or unicasting, employed singly or in combination. In general, a receiving unit in the network listen for signals on a given channel, and upon receipt of a candidate signal parses the signal header for initial evaluation to determine whether or not the signal is for the receiving unit. In broadcast, the signal does not contain specific addressing information of an intended receiver and any receiver capable of reading the signal can record the signal, whereas as in multicasting the signal contains address information to identify a receiver group, and in unicasting the signal contains address information to identify a single receiver. If a receiver receives a signal which includes an address different from its own address, it will disregard the signal.
A network of consumption meters may comprise a large number of individual units since every household in an area may contain one or more meters which communicate data back to a central unit, and it is normally a considerable communication task to individually communicate with each consumption meter in a given network. To reduce the total time of sending out information to every meter in a network, broadcasting can be used since it is a simple means for sending the same information out to a large number of receivers. It however comes with the expense of a limited control over the transmission since broadcasting is a unidirectional communication path. If it is important to more tightly control the transmission, unicast or multicast can be employed in a bi-directional manner, but at the expense of a high network load.
Network enabled consumption meters are typically equipped with an embedded microprocessor which contains control software, often referred to as firmware, and which is capable of performing various processing tasks based on the control software and on other software entities. Advantageously, the control software and possibly other software entities can be updated remotely via the network. To remotely update the control software of a consumption meter, a relative large amount of data needs to be transmitted to a large number of meters in the network. During an update process, there is thus a risk that some parts of the data are lost in the transmission, for example due to transmission collision. In connection with a control software upload, or upload of other core software entities, it is important that all data are received at each updated meter, otherwise it is not possible to make the exchange with the updated version of the software. Consequently an approach should be implemented which can guarantee this. However, there is generally a desire that the time it takes to update a group of consumption meters should be kept as low as possible.
WO 2005/015890 in the name of Enel Distribuzione discloses a system for remote distribution of program data to consumption meters. In a first phase of the update process unicasting is employed in order to individually send information to each meter relating to which data it should receive in order to receive a complete set of program data. In a second phase, the program data is broadcast. In a third phase each meter is queried successively for receipt status, and missing program data packets are re-broadcast. The third phase is continued until all meters report that they have received complete program data. In this system, a dedicated session between the data distributor and each meter is established a number of times, each followed by a broadcast of missing program data.
A similar approach is disclosed in WO 2008/130991 in the name of Elster Electricity.